Data storage devices, for example, smart cards containing bank account details in the form of data values stored in integrated circuit (IC) memory addresses, are at risk from fraudulent optical detection by the removal of the plastic encapsulation around the IC, etching away covering layers and applying a selectively absorbable stain to render the memory data optically visible.
It is known that address encrypting arrangements may be used, which result in the data values being arranged non-sequentially within the IC memory. The data therefore appears meaningless if optically analysed, but can be legitimately accessed through the address encrypting arrangement. A problem with this arrangement is that by performing the same optical detection techniques as mentioned above, one could learn the encrypting details on which the encrypting arrangement is based and thus could make sense of the data within the IC.
This invention seeks to provide a data storage device in which the above mentioned disadvantage is mitigated.